The present invention describes a composition and process using the composition for removal of metal ions from aqueous process solutions.
Various metals are used in many useful industrial processes. For example, silver is used in many image-forming industrial processes, such as photography, thermography, and photothermography. Such processes, however, result in waste solutions containing metal ions at levels that may be undesirable to the environment. In addition, many countries now have laws that control the levels of certain metal ions that can be released into the environment. Since commercial disposal of large volumes of untreated waste solutions can be costly, there has been a concerted effort to treat the waste solutions in a cost effective manner. Furthermore, these metals can be of sufficient value to justify their recovery.
Metals have been removed from aqueous waste solutions utilizing processes such as ion exchange, electrolysis, and settling. However, all of these known processes have their limitations. Ion exchange is costly, slow and impractical. The ion exchange resins are expensive because they require complex and sophisticated fabrication processes. Some of this cost can be recouped by regenerating the ion exchange resins. However, the waste solutions produced during regeneration typically have to be treated. Similarly, electrolysis is also costly due to maintenance, resource requirements, and energy input. Electrolysis is also very sensitive to contaminants and generally provides ineffective levels of metal recovery.
Settling processes typically use one or more agents that transform the metals into materials that are no longer soluble in the system and settle to the bottom of the tank. However, currently known settling processes have the following limitations. Undesirably large amounts of sludge, which cannot be regenerated, can be formed. Some settling processes require heating to very high temperatures, e.g., greater than 80xc2x0 C., to provide useful results. Still others require the use of a change in pH to cause the transformation of the metal into an insoluble material.
Accordingly, there is a need for effective recovery of metal ions from aqueous waste solutions (hereafter also referred to as aqueous process solutions).
The present invention is directed to a composition and the use of the composition in a process that effectively removes metal ions from aqueous process solutions.
The composition includes a non-metallic compound, which is capable of forming a complex with a metal ion, entrapped within or supported onto a support material. In one embodiment of the present invention the non-metallic compound is a thiuram. In another embodiment of the composition, the composition further includes a dithiocarbamate entrapped within or supported onto the support material. These compositions can be obtained by a process of contacting a non-metallic compound composition with a support material. The non-metallic compound composition can include the thiuram or a combination of thiuram and dithiocarbamate. The present invention is also directed to the composition obtained by this process.
In another aspect of the present invention, a process is disclosed for removing metal ions from an aqueous process solution utilizing the compositions of the present invention. The process includes reacting the metal ions in the aqueous process solution with a treatment composition having a non-metallic compound entrapped within or supported onto a support material. The metal ions and the non-metallic compound can form an organometallic complex. It is preferred to have a wetting agent present in the aqueous process solution.
The present invention is also directed to a product, an organometallic composition, obtained from the processes described above. The organometallic composition includes an organometallic complex entrapped within or supported onto a support material, wherein the organometallic complex includes a non-metallic compound associated with a metallic ion.